Http://teachers.yourhomework.com/blowe/1 Today's Agenda.w 1/19/11 Recall 1 & 2 Get your comp books out before the bell rings Continue Semester Review Start.

http://teachers.yourhomework.com/blowe/ 1

Today's Agenda .w 1/19/11Recall 1 & 2

Get your comp books out before the bell rings

Continue Semester Review

Start studying for the Chem department final which will be on Monday January 24, 2011. There will be another class final as well.

Make sure to have a good book to read and pass time.

04/20/23

Chemistry Department Final

The Chemitry department final is on Monday January 24th. This will be closed notes and book.

There will be an additional Chem test on your “final” day based on material this semester. This one will be open notes and book.

04/20/23

Recall 1

Convert the following numbers into scientific notation

①7654

②0.000452

③5754.32

④0.08999

04/20/23

7.654 x 103

4.52 x 10-4

5.75432 x 103

8.999 x 10-2

Recall 2

Convert the following numbers from scientific notation to standard form

①9.99 x 102

②3.156 x 10-3

③7.23 x 105

④3.6 x 10-2

04/20/23

999

0.003156

723000

0.036

Temperature Conversions

To Fahrenheit from Celsius

F = C x (9/5) + 32

Example:

What is 32°C in °F?

F = 32 x (9/5) + 32

F = 57.6 + 32

F = 89.6°F

To Celsius from Fahrenheit

C = (F - 32) x (5/9)

Example:

What is 75°F in °C?

C = (75 - 32) x (5/9)

C = (43) x (5/9)

C = 23.9°C04/20/23

Temperature Conversionsto Kelvin

To Kelvin from Celsius

K = C + 273

Example:

What is 32°C in K?

K = 32 + 273

K = 305 K

To Celsius from Kelven

C = K - 273

Example:

What is 50 K in °C?

C = 50 – 273

C = -223°C

04/20/23Always change from Fahrenheit to Celsius then to Kelvin

Dimensional analysisVolume = How much space something takes up

Mass = How much something weighs

Density = Mass/Volume

Example:

A block of Aluminum is 3 cm x 4 cm x 5 cm and has the density of 2.7 g/cm3. What is the mass of this block?

Volume is 3 x 4 x 5 = 60 cm3

Mass = Density x volume

Mass = 2.7 g/cm3 x 60 cm3 = 162 g

Dimensional analysisGraduated cylinders can be used to find the

volume of an object.

Volume = Final measurement – Initial measurement

Example:

A graduated cylinder first measures 40 mL. After an object is dropped in it then reads 62 mL. What is the volume of the object?

V= 62 – 40 = 22 mL

BTW mL = cm3

Protons, neutrons, & electrons

Protons are positively charged particles in the center of atoms (p+)

The number of protons an atom has equals the Atomic Number of an Atom.

This is the top number on a periodic table

Ex: How many protons does Scandium have?

21

Elecrtrons are negativily charged particles that orbit the nucleus of an atom (e-)

The number of electrons equals the number number of protons in a neutral atom

When an atom has an extra electron(s), there is a negative net charge of an Atom

Ex: F1-, has one extra electron

Ex: Mg2+ has two missing electrons

04/20/23

Protons, neutrons, & electrons

Neutrons have no charge and are about the same size as protons. They are in the nucleus of an atom

The number of neutrons is the given atomic weight minus the atomic number.

Ex: A sample of Carbon is 14 amu (atomic mass units). How many neutrons are present?

14-12=

2 neutrons

pp

04/20/23

Atomic Structures SymbolsHydrogen

HNumber of Protons

Atomic mass

1 – 1 = 0 neutrons

H1

1

How many neutrons in this atom?

-EX-

-example-

Bk250

97How many neutrons in this atom?

250 – 97 = 153 Neutrons

Berkelium

The Bohr Model

• Niels Henrik David Bohr came up with the Bohr Model

• The Bohr Model looks like a mini solar system with the nucleus as the sun and electrons as planets.

Hydrogen Bohr Model

The Bohr Model

• Electrons orbit the nucleus in different levels.

• The first level is the closest to the nucleus and it can only hold 2 electrons.

• The second and third come after the first and are farther away, they can hold 8 electrons each.

• The 4th orbit can hold 18 electrons

18

8

82

Bohr example

11 Atomic Number

•Therefore I know this atom has 11 protons and because it’s neutral, 11 electrons

Sodium

11p•There are 12 neutrons because the Atomic Mass 22.99 rounded up to 23 (which you look up on your periodic table) minus the atomic number 11 equals 12

12n

2e

8e

1e

1st Orbital Shell

2nd

3rd

Average Atomic Mass

• Remember, isotopes are atoms with different numbers of neutrons

• Average Atomic mass = (mass) (abundance) + (mass) (abundance) +….

• Average Atomic mass = (mass) (%) + (mass) (%) +….

• You have to change % into decimalsi.e. 89.5% = .895 i.e. 12.4% = .124 i.e. 7% = .07

Example

• There are two isotopes of chlorine:chorine-35 (75.8%) and chorine-37 (24.2%)

a) How many neutrons does each isotope have? (Chorine has a atomic number of 17)

Chorine-35 has 18 neutrons

35 – 17 = 18 neutrons

Chorine-37 has 20 neutrons

37 – 17 = 20 neutrons

Example continued

• b) What is the average atomic mass of chlorine? (chorine-35 (75.8%) and chorine-37 (24.2%))

•Average Atomic mass = (mass) (%) + (mass) (%) +….

•Average Atomic mass = (35) (.758) + (37) (.242) = 26.53 + 8.95 = 35.48

Writing the Notation!

Write the electron configuration for the atom with atomic number 20

Ca has atomic number 20 (from the periodic table). 20 protons means there's 20 electrons.

The order of orbitals are:1s 2s 2p 3s 3p 4s 3d 4p

1s 2s 2p 3s 3p 4s 3d 4p2 2 6 62 2

You can check that we got 20 electrons

HomeworkBegin to start reviewing for the semester final

Some strategies that may help:

• Read over your notebook

• Try and find the chapters in the book that correspond to your notes and practice questions.

• Go over recalls and examples in your notebook

• Take time to memorize names like the difference between Nitrate and Nitride!

http://teachers.yourhomework.com/blowe/ 2004/20/23